Because of their intimate association with soil contaminants, we HYPOTHESIZE that the diversity[unreadable] [measured as richness and evenness) of the metabolically-active fraction of the soil bacterial community[unreadable] serves as a biomarker of the threat to human health from PAHs and heavy metals polluting Superfund sites.[unreadable] To challenge this hypothesis, we will address three SPECIFIC AIMS: (1) Identify correlations between the[unreadable] results of molecular biology-based measures of bacterial diversity and analytical measures of PAHs and[unreadable] heavy metals during soil ageing and bioremediation of mock Superfund sites; (2) Demonstrate novel[unreadable] molecular biology-based assays to assess the diversity of the metabolically active fraction of the bacterial[unreadable] community in situ; and (3) Demonstrate ecological models to predict soil bacterial community diversity under[unreadable] the influence of mixtures of heavy metals and PAHs. The APPROACH includes: (i) operating mock[unreadable] Superfund sites; (ii) T-RFLP and (iii) whole cell FISH to measure bacterial diversity; (iv) identifying[unreadable] predominant bacterial populations using clone libraries; (v) evaluating the impact of PAH and heavy metals[unreadable] on ribosome genesis; (vi) identifying heavy-metal responsive genes using microarrays; (vii) evaluating[unreadable] metagenomics of PAH degradation; (viii) evaluating real-time PCR to quantify heavy-metal and PAHresponsive[unreadable] genes; (ix) adapting ecological models to predict bacterial diversity; (x) comparing experimental[unreadable] measures of diversity with model predictions; and (xi) evaluating optimum nutrient amendments predicted[unreadable] with the resource-ratio theory. This project is INNOVATIVE because we are using molecular biology-based[unreadable] measures of bacterial diversity as a diagnostic tool to predict the threat to human health at Superfund sites[unreadable] (i.e., bacteria as sentinels for pollution). We expect that the positive findings of this study can be used to[unreadable] evaluate the potential for success of bioremediation strategies as well as to establish an effective endpoint of[unreadable] bioremediation (i.e., when appropriate bacterial diversity has been re-established and the threat to human[unreadable] health significantly reduced).